1. Field of the Invention
The present invention relates to a system and a method for initializing an apparatus for transferring asymmetrical data, and more particularly, to a system and method for reducing initialization time of an apparatus used for transferring asymmetrical data using previously stored characteristics of the transfer line.
2. Description of the Related Art
A system for transferring asymmetrical data is used as part of a high speed MODEM having a transferring speed of at least 9,600 bps. The bandwidth of a telephone line--connected to the MODEM--is divided into a low speed communication line and a high speed communication line, which are both asymmetrical communication lines. Initially, data is transferred at a speed of about 300-450 bps in the low speed communication line and later at a speed of at least 9,600 bps in the high speed communication line. The data is received and transferred simultaneously by the above mentioned division of the bandwidth into two.
FIG. 1 is a block diagram of a system for transferring asymmetrical data. A mother apparatus 100 is connected to a child apparatus 102 by a telephone line 101. The mother apparatus receives digital data from and transfers data to the child apparatus 102. In this example, the mother apparatus 100 is installed in a telephone office. The child apparatus 102 is installed in a subscriber's home. occasionally data transfer may be affected by an interruption in the power supply to the mother apparatus 100 or the telephone line 101. In such a case, the apparatus for transferring asymmetrical data shown in FIG. 1 is initialized. The initialization takes place after the interruption ceases.
FIG. 2 is a flowchart showing a conventional method of initializing the apparatus shown in FIG. 1. In this flowchart, a transfer line uses a frequency band between 30-1104 kHz which has been divided into 248 sub-channels (4.3125 kHz per sub-channel) to transmit data between a mother and a child apparatus.
In step 220 the telephone line is optimized by the mother apparatus 100 transferring a test signal to the child apparatus 102, as part of a basic communication. In step 230, the attenuation of the noise and signal in each of the 248 sub-channels constituting the frequency band is analyzed. In step 240, 0-15 data bits to be transferred are assigned to each of the sub-channels using the analysis made in the step 230. In step 250, the assigned data bits are transferred to the child apparatus 102--thereby performing a normal communication.
In the above-mentioned initialization process of FIG. 2, unnecessary time is consumed since the characteristics of the frequency band, used to transmit data on the transfer line, are examined during every initialization after an interruption.